System and method for using microsaccade dynamics to measure attentional response to a stimulus

ABSTRACT

A system and method for determining a subject&#39;s attentional response to a stimulus. The method includes measuring microsaccadic eye movement dynamics of the subject, detecting whether a microsaccadic signature (a suppression in microsaccadic rate) is present in the measured microsaccadic eye movement relative to a time of the stimulus, and correlating the subject&#39;s attentional response to the stimulus based on the detection. The method further includes determining that the stimulus was sensed if the microsaccadic signature is present and determining that the stimulus was not sensed if the microsaccadic signature is absent.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/359,235 filed May 19, 2014, which represents the national stage entryof PCT International Application No. PCT/US2012/066462 filed Nov. 23,2012, which claims the benefit of U.S. Provisional Patent ApplicationSer. No. 61/562,576 filed on Nov. 22, 2011, the disclosures of which areincorporated herein by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

The present application is directed to monitoring eye movements todetermine a subject's attentional response to a stimulus. In particular,the present application is directed to analyzing microsaccade dynamicsfor an exhibited microsaccadic signature to determine whether a subjectsenses a stimulus.

Little is known about the neuroscience of emotional manipulation withrespect to cognition and attention. More specifically, there arecurrently no objective measures to determine how emotions aremanipulated by narrative elements, such as rhetoric, media events,propaganda, unfolding events on the battlefield, or how narrativeelements actually influence observers. Therefore, it would be desirableto provide a method and system for objectively measuring a subject'sresponse to a stimulus, such as a narrative that invokes an emotionalthreat.

SUMMARY OF THE INVENTION

The present invention provides a method for determining a subject'sattentional response to a stimulus. The method includes measuringmicrosaccadic eye movement dynamics of the subject, detecting whether amicrosaccadic signature is present in the measured microsaccadic eyemovement relative to a time of the stimulus, and correlating thesubject's attentional response to the stimulus based on the detection.The method can further include determining that the stimulus was sensedif the microsaccadic signature is present and determining that thestimulus was not sensed if the microsaccadic signature is absent.

A system in accordance with the present invention includes an eyetracking device and a host operably connected to the eye trackingdevice. The eye tracking device is capable of detecting eye movementtraces and the host is configured to receive the eye movement tracesfrom the eye tracking device. The host is further configured to measuremicrosaccadic eye movement dynamics of the subject based on the eyemovement traces, detect whether a microsaccadic signature is present inthe measured microsaccadic eye movement relative to a time of thestimulus, and correlate the subject's attentional response to thestimulus based on the detection.

A method in accordance with the present invention includes determining asubject's attentional response to a stimulus. The method includesreceiving eye movement traces of the subject over a time periodincluding a time of the stimulus, determining, from the eye movementtraces, a microsaccade rate of the subject over the time period, anddetecting whether a microsaccadic signature is present in the eyemovements relative to the time of the stimulus. The microsaccadicsignature can be a suppression of the microsaccade rate below a baselinerate. The method can further include generating a report indicating thesubject's attentional response to the stimulus based on the detection.

A method in accordance with the present invention includes determining asubject's attentional response to a stimulus. The method includesmonitoring eye movements of the subject over a time period including atime of the stimulus, measuring microsaccadic eye movement dynamics ofthe subject based on the eye movements, and calculating, from themicrosaccadic eye movement dynamics, microsaccade rate over a timeperiod including a time of the stimulus. The method can further includedetecting whether a microsaccade rate suppression event is present inthe measured microsaccadic eye movement relative to the time of thestimulus, determining the subject's attentional response to the stimulusbased on the detection, and generating a stimulus detection thresholdbased on the determined attentional response to the stimulus. Thestimulus detection threshold can indicate a probability of the subjectresponding to the stimulus based on information about the stimulus.

The foregoing and other aspects and advantages of the invention willappear from the following description. In the description, reference ismade to the accompanying drawings which form a part hereof, and in whichthere is shown by way of illustration a preferred embodiment of theinvention. Such embodiment does not necessarily represent the full scopeof the invention, however, and reference is made therefore to the claimsand herein for interpreting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation of microsaccade rate over time,illustrating an exhibited microsaccadic signature.

FIG. 2 is a flow chart setting forth the steps of a method fordetermining attentional response to a stimulus, in accordance with thepresent invention.

FIG. 3 a is a graphical representation relating microsaccade suppressioneffect and percent conscious detection to duration of a stimulus.

FIG. 3 b is a graphical representation relating microsaccade suppressioneffect and percent conscious detection to threat level of a stimulus.

FIG. 4 is a schematic view of a system according to the presentinvention.

FIG. 5 is a schematic view of another system according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally provides a method monitoring eyemovements of a subject to determine the subject's attentional responseto a stimulus. Such eye movements can include microsaccade dynamics, andmore specifically, microsaccadic rate over a time period (including thetime of stimulation). The microsaccadic rate can be analyzed to detectwhether a microsaccadic signature was elicited within the time period.If no microsaccadic signature is observed, the stimulus was not sensed(that is, unconscious or no response). If the microsaccadic signature isobserved, the stimulus was sensed and either a subconscious or consciousresponse may be concluded. Furthermore, if the microsaccadic signatureis observed, properties of the microsaccadic signature can be analyzedto determine the magnitude of the response. This method can serve as anobjective measurement of attentional response to a stimulus because, asfurther discussed below, microsaccades are involuntary movements thatcannot be forced by the subject.

In a subject's visual field, visual attention may be focused accordingto the attentional spotlight. More specifically, the attentionalspotlight can enhance perception at a given spatial focus within thevisual field or can selectively enhance features of interest within thevisual field. Furthermore, the attentional spotlight can suppress allareas outside the feature of interest. For example, when a human fixatestheir gaze, the eyes are only actually fixated 80% of the time, whilesaccades (quick, simultaneous movements of both eyes in the samedirection) and microsaccades (involuntary saccades that occur duringattempted fixation of the eyes, which are usually less than 1 degree inmagnitude) occur the other 20% of the time. During this fixated gazewhen the subject is attending covertly to a position away from thetarget of fixation, dual nodes of activity are generated in the superiorcolliculus (an area of the brain that targets both eye movements andattention). The first node of activity is at the center of the superiorcolliculus's visual map, which maintains fixation and targets fixationalmicrosaccades. The second node of activity is in the periphery of thesuperior colliculus's map at the position of the attentional spotlight.When the superior colliculus is readout by brainstem mechanisms, thedual nodes activity are combined, resulting in microsaccades biasedtowards the location of the attentional spotlight. In other words, nomatter where a subject fixates on an image, the rate and direction ofmicrosaccades is influenced by the presence and position of thesubject's target of interest on the image. The subject may overtlyattend the interested target (by looking right at it) or covertly attendthe target (by looking away from the target and secretly payingattention to the target). Even when covert attention is engaged,microsaccades are biased in a direction towards the attended region ofinterest in an involuntary and unconscious manner.

As described in U.S. Pat. No. 7,857,452, the entire contents of whichare incorporated herein by reference, eye movements can be monitored todetect this bias. Generally, these detection methods include tracking asubject's eye position and detecting microsaccades from eye positiontraces. Example algorithms for detecting microsaccades objectively fromeye position traces (e.g., from video, eye coil, optical, or othersuitable tracking methods) include the Martinez-Conde and Macknikalgorithm (Martinez-Conde S., Macknik S. L., Hubel D. H. (2000) NatureNeuroscience, incorporated herein by reference) and the Engbertalgorithm (Engbert R., Kliegl R. (2003) Vision Res 4:1035-1045,incorporated herein by reference). Next, microsaccade position anddirection can be determined and the subject's region of interest can bedetermined using this information. Several different methods can be usedto make this determination. For example, one method includes determiningtrajectories of tracked microsaccades and extrapolating the trajectorieswithin the subject's visual field to determine areas of trajectoryintersection. A subject's region of interest is likely in regions wheremore intersections exist. Furthermore, the trajectories can betriangulated to determine the likely region of interest. Accordingly,because microsaccades are involuntary movements that are invisible tothe subject who is making them, the subject's attentional focus (regionof interest), whether covert or overt, can be objectively andnon-invasively determined.

When the subject's attentional spotlight is activated, for example inresponse to a stimulus, the result is that microsaccades exhibit astereotypical behavior—a “microsaccadic signature”—in which they aresuppressed and then often rebound in rate. This is illustrated in FIG. 1, where at time t=0, microsaccadic rate drops significantly below anormal rate (that is, suppresses), rapidly increases above the normalrate (that is, rebounds), then returns back to the normal rate. Astimulus that activates the attentional spotlight can refer to anysensory stimulus (visual, auditory, olfactory, etc.), or cognitiveprocess, that attracts attention of the subject to a target area in thesubject's field of view. This can be as simple as an on/off-typestimulus, such as a flash of light, a flash of an image on a screen inthe subject's field of view, an object appearing in the subject's fieldof view, etc. This can also refer to a target of interest in thesubject's field of view that invokes an emotional response, for examplein conjunction with narrative influence (such as a verbal emotionallycharged threat or influential statement). In addition, the magnitude ofthe microsaccadic signature (for example, the magnitude of thesuppression) may generally indicate the magnitude of the attentionalspotlight. For example, the primary physiological effect of emotions isthat they drive cognitive brain systems to focus spatial attention.Thus, invoking an emotional response can affect the location andmagnitude of attentional spotlight, where a larger emotional responsecan invoke a larger suppression.

In light of the above, the present invention provides a method, as shownin FIG. 2 , for objectively determining whether is stimulus is detectedby a subject. The present invention further provides a system forcarrying out this method, as illustrated in FIGS. 4 and 5 and furtherdescribed below. Generally, the method can include measuring a subject'smicrosaccade dynamics over a time period and determining whether astimulus presented within that time period was sensed or not sensed bythe subject. More specifically, as shown in FIG. 2 , a subject'smicrosaccade dynamics can be measured [process block 10]. Microsaccadedynamics can include microsaccade rate over a time period, for examplewherein a stimulus is presented within that time period. These dynamicscan be measured by monitoring eye movements and detecting microsaccadesfrom eye position traces, as discussed above.

The microsaccade dynamics can then be analyzed to determine if amicrosaccadic signature was present [process block 12]. This step can beperformed by determining a baseline or normal microsaccade rate, anddetermining a relatively quick drop or suppression from the normal ratewithin the time period. On average, a human's normal microsaccade rateis about one microsaccade per second. For example, as shown in FIG. 1 ,the baseline microsaccade rate is relatively steady around onemicrosaccade per second, then at time t=0 (that is, time of stimulus),the microsaccade rate drops to almost zero (in less than 200milliseconds), rebounds above the baseline rate, and returns back to thebaseline rate. This entire microsaccadic signature occurs within about500 milliseconds. In some applications, the microsaccadic signature canbe determined by comparing the measured microsaccade rate topredetermined or stored thresholds.

If the microsaccadic signature is not detected, the stimulus was notsensed by the subject (in other words, the subject's brain wasunconscious to the stimulus) [process block 14]. A report indicatingthis conclusion (that is, “not sensed” or “unconscious”) can then begenerated and displayed and/or recorded [process block 16]. If themicrosaccadic signature is detected, the stimulus was sensed by thesubject, either consciously or subconsciously [process block 18]. Insome cases, a report indicating this conclusion (that is, “sensed”) canthen be generated and recorded and/or displayed [process block 20]. Inaddition, user input can be retrieved [process block 22]. This userinput can include feedback from the user regarding whether theyacknowledged a stimulus or not. Based on this user input, one canconclude whether the stimulus invoked a conscious response or asubconscious response [process block 24]. More specifically, if userinput indicated the stimulus was detected, then the stimulus wasconsciously detected [process block 26]. A report indicating thisconclusion (that is, “conscious response”) can then be generated anddisplayed and/or recorded [process block 28]. If user input indicatedthe stimulus was not detected, then the stimulus was only subconsciouslydetected [process block 30]. A report indicating this conclusion (thatis, “subconscious response”) can then be generated and displayed and/orrecorded [process block 32].

In some applications, generated reporting data from the above method,for example performed on one or more subjects, can then be used toprovide general probabilities of a subject's attentional response to agiven stimulus. For example, FIG. 3 a graphically illustratesattentional response invoked by flashes of light (that is, stimuli) ofvarious durations. Generally, at low durations, the luminance of theflash is too low for a subject's brain to detect; however, at longdurations, the flash can be easily and consciously perceived.Accordingly, detection can improve as a function of stimulus duration.Thus, if the stimulus is a long flash of light (that is, long duration),the subject can detect it consciously and there will be a detectablemicrosaccadic signature, thereby illustrating a conscious response. Avery short flash will result in neither conscious detection of the flashor an elicited microsaccadic signature, thereby illustrating that thebrain is unconscious to the stimulus. A medium length flash will resultin high probability of a microsaccadic signature, but lower probabilityof conscious detection. This can be referred to as a subconscious eventbecause the brain “sees” the flash of light (otherwise, there would beno microsaccadic signature), but there was no conscious perception ofthe flash of light by the subject.

More specifically, the x-axis of FIG. 3 a illustrates relative stimulusduration (short to long). The y-axis illustrates two variables:probability of microsaccade suppression effect (low to high percent) andprobability of conscious detection (low to high percent). Microsaccadesuppression effect with respect to stimulus duration is illustrated byline 34, and percentage conscious detection with respect to stimulusduration is illustrated by line 36. Thus, generally, the area to theleft of line 34 illustrates where the brain is unconscious to thestimulus (occurring at shorter stimulus durations), the area to theright of line 36 illustrates conscious detection of the stimulus(occurring at longer stimulus durations), and the area between lines 34and 36 illustrates subconscious detection, where a microsaccadicsignature is present, but conscious detection is not.

By way of example, at duration d1, there is about a 50% chancemicrosaccadic suppression will be invoked (point A), but a much smallerchance that conscious detection will occur (point B). At duration d2,there is a very high chance microsaccadic suppression with be invoked(point C), and about a 50% chance conscious detection will occur (pointD). It is noted that microsaccadic suppression effect may coincide withconscious perception, but it can never be higher (or else the stimulusis unattended and therefore invisible perceptually). In other words, thechance of conscious detection cannot be higher than the chance ofmicrosaccadic suppression. In addition, the lines 34 and 36 can befurther refined based on additional generated data.

In another example, FIG. 3 b graphically illustrates attentionalresponse invoked by stimuli of various emotional threat levels.Generally, at low threat levels, a microsaccadic signature is notelicited, illustrating no emotional response. High threat levels,however, can evoke a microsaccade suppression and a conscious or visibleemotional response. Thus, if the stimulus contains a high threat level,the subject will evoke a noticeable emotional response to the threat andthere will be a detectable microsaccadic signature, illustrating aconscious event. A stimulus with low threat levels will result inneither emotional response or an elicited microsaccadic signature,indicating the brain is unconscious to a perceived threat. A“middle-grade” threat can result in high probability of a microsaccadicsignature, but low probability of a conscious emotional response by thesubject. Similar to that discussed above, this can be referred to as asubconscious event because the brain elicits an emotional response(otherwise, there would be no microsaccadic signature), but there was noconscious emotional response by the subject.

More specifically, the x-axis of FIG. 3 b illustrates relative threatlevel (low to high). The y-axis illustrates two variables: probabilityof microsaccade suppression effect (low to high percent) and percentageof conscious detection (low to high percent). Microsaccadic suppressioneffect with respect to threat level is illustrated by line 38, andpercentage conscious detection with respect to threat level isillustrated by line 40. Thus, the area to the left of line 38illustrates unconscious, that is, no emotional response (occurring atlow threat levels). The area to the right of line 40 illustratesconscious perception or a visible emotional response (occurring at highthreat levels). The area between lines 38 and 40 illustratessubconscious detection, where a microsaccadic signature is present, butconscious perception is not. The lines 38 and 40 can be plotted andrefined based data from one or more subjects tested at different threatlevels, for example using the methods discussed above, thus providinggeneral probabilities of a subject's attentional response at a giventhreat level.

By way of example, at a lower threat level L1, there is about a 50%chance microsaccadic suppression will be invoked (point E), but a muchsmaller chance that conscious response will occur (point F). At a higherthreat level L2, there is a very high chance microsaccadic suppressionwith be invoked (point G), and about a 50% chance conscious responsewill occur (point H). In addition, the lines 38 and 40 can be furtherrefined based on additional generated data. In some applications,stimuli of different threat levels can include emotional images where,for example an emotional image of a person exhibiting cheerful or happybody language would be at a very low threat level and an emotional imageof a person exhibiting angry body language would be at a higher threatlevel.

In some applications, additional factors can be identified and analyzedin conjunction with the above-described method, such as othercharacteristics of microsaccade dynamics. In one example, the magnitudeof the microsaccadic signature (for example, the magnitude ofsuppression from the normal rate) can be determined and can becorrelated with a magnitude of the attentional response. With respect tothe threat-level example discussed above, a higher magnitude ofsuppression can illustrate a larger threat level sensed or perceived. Inanother example, microsaccadic directions can also be identified. Then,by triangulating the bias in microsaccadic directions, and bydetermining the occurrence and magnitude of the microsaccadic signature,the location of the subject's locus of attention and its magnitude ofattentional response can be identified with respect to a presentedstimulus. In other words, using the method of the present invention, onecan determine whether a stimulus was sensed, when it was sensed, andwhere in visual space the subject focuses upon sensing the stimulus.

Furthermore, in some applications, the method can further includepredetermined probability thresholds (such as those discussed above withrespect to FIG. 3 a or 3 b) to assess the reliability of the user inputgiven. Generally, self-reporting may be unreliable due to unconsciousand intentional criterion effects. However, the assessment ofmicrosaccade dynamics can provide an unbiased and objective conclusionas to whether a stimulus was sensed or not (for example, a terrorist maylie, but his or her microsaccades cannot). Furthermore, with the aid ofthe predetermined probabilities, one can estimate whether a subjectshould have consciously perceived a stimulus at a given level, duration,etc. Even in the event that the microsaccadic signature is equal toconscious perception (for example, a visible reaction was observed),this method still has the advantage that it is unbiased and objective.In addition, such conclusions can be determined secretly andnon-invasively, since eye movement and visible reactions can be observedfrom a standoff distance, as further discussed below.

Referring now to FIG. 4 , a system 42 for detecting and analyzing eyemovement of a subject to measure an attentional response of a subject 44is presented. The system 42 can include a host 46 operably connected toan eye tracking device 48, a display 50, and a user interface 52. Thehost 46 can include one or more processors 54 operating under control ofone or more computer programs 56 loaded from a non-transitory computerreadable medium (memory) 58. As used herein, reference to a stepperformed by a computer program 56 is also a reference to the processor54 that performed that step, for example in accordance with the processblocks discussed above. Example tracking devices 48 for use with thepresent invention can include the EyeLink II by SR Research(http://www.sr-research.com/fixed tech spec.php) or other equivalent eyetracking systems such as the IVIEW™ HI-SPEED 1250 tracking system bySensoMotoric Instruments(http://www.smivision.com/en/eye-gaze-tracking-systems/products/iview-x-hi-speed.html).

The system 42 can operate by presenting a stimulus, such as an image, tothe subject 44 through the display 50. For example, one of theprocessors 54, such as display processor, can retrieve one or morestored image files 60 from memory and present the images of a narrativeto the subject on the display 16 either statically or dynamically. Inthis regard, the image files may each contain one or more static imagesor video sequences of images. In some cases, each of the image files 60may include one or more emotive elements 62, 64 within the images thatare intended to evoke a particular response along with the coordinatepositions of the elements within each of the images. Where the imagesare presented dynamically, the processor 54 can maintain an image table66 of image data including current positional information (such as x-ycoordinates) for each of the elements as they are moved around thedisplay 50. In some cases, the image files 60 also include related audioinformation. In such cases, the audio information can be presented tothe subject 44 as part of a narrative along with the images through thedisplay 50.

As the images are presented to the subject 44, the eye tracking device48 can detect the position and movement of the subject's eyes 68. One ofthe processors 54, such as a tracking processor, can receive a positionof the eyes 68, a distance between the subject 44 and the display 50 andcalculate a center of the field of view of the eyes 68 on the display 50under an appropriate coordinate system (such as x-y coordinates of theeye position on the display 50). Once calculated, the tracking processor54 can receive the then-current image table 66 from the displayprocessor 54, combine the data as a snapshot in time of eye positionversus image data, and saves the data in a file 70. The measurement ofmicrosaccade dynamics and analysis of microsaccade dynamics, such asdeterminations of microsaccadic signature or determinations of foci ofattention, as described above with respect to FIG. 2 , can be executedby one of the processors 54.

In addition, the subject 44 can provide user input through the userinterface 52. For example, the subject 44 can press a button whenever astimulus is acknowledged (whenever the subject sees an image). This userinput can be analyzed in conjunction with time of stimulus and/or thedeterminations described above through one of the processors 54.Furthermore, reports, such as those described above with respect to FIG.2 , can be generated, stored, and/or displayed (via the display 50 or adifferent display). Accordingly, the system of FIG. 4 can be used toperform the method described above for detecting and analyzing eyemovement of a subject to measure an attentional response of the subject44. In some applications, the system of FIG. 4 can be used to generatereporting data for use in preparing probability charts and thresholds,as described above. Furthermore, in some applications, a processor 56can analyze the generated reporting data to automatically prepare and/orrefine the charts and thresholds. These charts and thresholds can thenbe stored in a file 72.

In one specific example, the system of FIG. 4 can be used as a flightsimulator system. By monitoring a subject's eye movements with respectto images or videos presented to the subject, valuable data can begenerated. For example, the system can detect when a subject notices athreat relative to when the threat is displayed to the subject.

In some applications, as shown in FIG. 5 , another system 42 of thepresent invention can include an eye tracking device 48 and a host 46with one or more processors 54 and memory 58 including one or morestored computer programs 56 and/or files 70, 72. The system 42 of FIG. 5can be used to monitor eye movements to detect the presence or absenceof microsaccadic signatures in response to outside stimuli (that is,stimuli not generated by the host 46). The system of FIG. 5 can also beused to monitor visible emotional responses to such stimuli (which maybe used as user input), either through the video eye tracking device ora different form of eye tracking device (not shown). As a result, thesystem 42 of FIG. 5 can be used to monitor the subject from a standoffdistance by using, for example, a telescopic lens with a video eyetracking system, for example without the subject's knowledge, todetermine the subject's attentional response to a stimulus. For example,the subject's microsaccade dynamics can be measured and recorded withina time period including, for example, each time a microsaccadicsignature was present and the time of occurrence. This recorded data canthen be analyzed in conjunction with any visual emotional responsesobserved and/or knowledge of nearby events at the time of occurrence.

The present invention has been described in terms of one or morepreferred embodiments, and it should be appreciated that manyequivalents, alternatives, variations, and modifications, aside fromthose expressly stated, are possible and within the scope of theinvention.

The invention claimed is:
 1. A method for determining a subject'sattentional response to a stimulus, the method comprising the steps of:receiving eye movement traces of the subject over a time period, whereinthe stimulus is introduced after the time period has begun; determining,from the eye movement traces, a microsaccade rate of the subject overthe time period; detecting whether a microsaccadic signature is presentin the eye movements relative to the stimulus being introduced, themicrosaccadic signature being a suppression of the microsaccade ratebelow a baseline rate; and generating a report indicating the subject'sattentional response to the stimulus based on the detection, whereingenerating the report includes generating reporting data classifying thesubject's attentional response to differentiate between one of anunconscious response, a conscious response, and a subconscious response.2. The method of claim 1, wherein the baseline rate is a predeterminedthreshold obtained from a host device.
 3. The method of claim 1 andfurther comprising receiving user input regarding whether the stimulusis acknowledged by the subject and correlating the subject's attentionalresponse to the stimulus based on the detection and the user input. 4.The method of claim 1 and further comprising measuring a magnitude ofthe detected suppression as a difference between a suppressed rateduring the detected suppression and the baseline rate and correlatingthe magnitude of the detected suppression to a relative magnitude ofattentional response.
 5. The method of claim 4, wherein generating thereport includes indicating the relative magnitude of the subject'sattentional response.
 6. The method of claim 1 and further comprisingdetermining, from the eye movement traces, trajectories of microsaccadeswith respect to a field of view of the subject.
 7. The method of claim 6and further comprising determining, from the eye movements, adirectional bias of the microsaccades based on the trajectories andidentifying a location of attentional focus of the subject with thefield of view based on the directional bias.
 8. The method of claim 7,wherein generating the report includes indicating the identifiedlocation of attentional focus of the subject.
 9. The method of claim 1and further comprising presenting the stimulus to the subject throughone of an image and a video.
 10. The method of claim 1, whereinreceiving eye movement traces includes obtaining the eye movement tracesfrom an eye tracking device.
 11. The method of claim 10, whereindetecting whether the microsaccadic signature is present includesdetecting, by a host device in communication with the eye trackingdevice, whether the microsaccadic signature is present.
 12. The methodof claim 1, wherein receiving eye movement traces includes obtainingrecorded data of the eye movement traces.
 13. The method of claim 1,wherein receiving eye movement traces includes obtaining the eyemovement traces from one of an optical eye tracking device, an eye coil,and a video.
 14. The method of claim 1 and further comprising generatinga stimulus detection threshold, based on the detection, defining aprobability of the subject responding to a future stimulus.
 15. Themethod of claim 14, wherein the stimulus detection threshold includes afirst stimulus detection threshold defining a probability of asubconscious response and a second stimulus detection threshold defininga probability of a conscious response.
 16. The method of claim 1 andfurther comprising displaying the report on a display of a host device.